Web handling apparatus

ABSTRACT

Web handling apparatus pulls web from a supported roll at a selected speed. A brake is provided for controlling the roll speed and a sensor senses changes in the tension of the web caused by changes in the pulling force of the web. The brake is controlled in accordance with the output of the tension sensor so that the web is maintained substantially under constant tension. Also, the apparatus responds to the instantaneous size of the roll by modulating the braking means so that the drag force imparted by the brake to the web is substantially independent of roll size.

United States Patent 1191 3,519,213 '7/1970 'Hofmann et 31...; ..242/57Butler, Jr. etaltff v J [4 5] July 9, 1974 [54] WEB HANDLING APPARATUS1223,35 I Eruton 3, 6 .45 [75] Inventors: 5 5m; f gg z i ggzgfi3,713,600 1/1973 M ifri ay et al. 242/5 8.4

s 9 9 both of Mass; August R. Rump, I Chicago, 111.; Rudy R. Arendt,South Primary Exammerbeonard Chnsflan wales, NY. Attorney, Agent, orFirmCesar1 and McKenna [73] Assignee: Butler Automatic lnc., Canton,Mass- 57 ABSTRACT [[22] med: 1972 Web handling apparatus pulls web froma supported [21] Appl. No.: 236,122 roll at a selected speed. A brakeisprovided for controlling the roll speed and a sensor senses changes in,7 the tension of the web-caused by changes in the pull- 1188]. I forcef h Th b k i controlled in accor. 1 w dance with the output of thetension sensor so that the 4 3 5 6 .web is maintainedsubstantially underconstant tena 1 sion. Also, theapparatus responds to the instanta- 1neous size of the roll by modulating the braking means [56] Referenc sothat the drag force imparted by the brake to the UNITED STATES PATENTSweb is substantially independent of roll size.

19 Claims, 2 Drawing Figures iv 56 All; Yo 66 6 4 I J v$01.. I 0 o 0VALVE L T PRINTING STATION 1-5; W rnzss as l 42 A 42 @coNTRoL CONSOLEBACKGROUND or THE INVENTION This invention relates to web handlingapparatus. It relates more particularly to a system for controlling webtension in such apparatus.

The apparatus with which we are concerned here is used to provide webuninterruptedly to machines which consume the web at high speed,- aprinting press, for example. The apparatus is designed to automaticallysplice the leading end of a roll of ready web to the trailing end of adepleted roll of running web and to deliver the web continuously in acontrolled fashion to the web-consuming machine. In order to accomplishthis, the apparatus includes an accumulator situated between the splicerand the web-consuming machine.

When the running web is stopped to splice its trailing end to the readyweb, there is enough material in the accumulator to supply the needs ofthe web-consuming machine until the ready web roll is accelerated torunning speed after the splice is made.

A conventional machine of this type is disclosed in U.S. Pat. No.3,305,189 and the present invention will be described in terms of amachine of that type.

. Basically, the apparatus includes supports for a pair of web rolls,one of which is running and one of which is at'the ready. The runningweb is conducted into an accumulator and the web material leaving theaccumulator travels into the web-consuming machine. The accumulator iscomprised of a set of fixed rolls and a movable dancer carrying a secondset of rolls. The web is looped between the fixed rolls and the dancerrolls, forming a series of bights. The amount of material in theaccumulator is controlled by moving the dancer toward or away from theset of fixed rolls. In other words, as the dancer moves further awayfrom the set of fixed rolls (i.e., upward), theamount of material in theaccumulator increases, and vice-versa. In operation, the dancer isbiased away from the fixed rolls under constant pressure and is causedto move by changes in the tension in the web. 7

Usually, web is pulled from the running roll by a pulling roll in theweb-consuming machine at a constant rate whose value depends upon therequirements of the webconsuming machine. The running supply roll isbraked in a controlled fashion to maintain the proper web tension. Inthe apparatus illustrated in the above patent,the amount of brakingforce applied to the running web roll, i.e., the amount of tensionimparted to the web, is determined by the position of the dancer in theaccumulator which, as pointed out above, reflects web tension.

the needs of the web-consuming machine when the running roll is stoppedfor splicing. A

These prior system work well at relatively low web speeds. However, athigher speeds, on the order of 1,500 feet per minute, certain problemsdevelop. More particularly, in an attempt to maintain constant webtension at these high speeds, the dancer tends to hunt about its zeropoint, causing unwanted web tension changes. This is due in large partto the inertia of the dancer and the delay between the time when thedancer issues a command signal to the brake and the time when the'brakeresponds. Also,.the running web supply roll is constantly decreasing indiameter so that its moment of inertia is constantly changing.Accordingly, when the brakes are applied, the-web tension is affecteddifi'erently, depending upon the amount of material remaining onthe-roll. In practice, this effect causes a gradual increase in webtension, with the result that the dancer moves down and reduces theamount of available material in the accumulator. Also, in the priormachines, there is a relatively long time delay between the variousevents which take place during the splicing cycle, and after splicingthere is inadequate SUMMARY or THE INVENTION Accordingly, this inventionaims to provide a web tension control system which operates reliably athigh web speeds.

As the dancer moves toward the set of fixed rolls (i.e., downward)indicating an increase in the web tension, the web braking force isreduced so that web runs into the accumulator at a faster rate, therebytending to move the dancer up away from the set of fixed rolls.Conversely, if the dancer moves upward, indicating a web tensiondecrease, the braking force on the running roll is increased to slowdown the rate at which web enters the accumulator. This tends to movethe dancer downward toward the set of fixed rolls. Thus, during normaloperationof the apparatus, the dancer seeks a zero position in anattempt to maintain substantially constant tension in the web. Thisposition is selected so that there is enough web in the accumulator tosatisfy Another object of the invention is to provide a web tensioncontrol system which maintains close control over web tensionimmediately before and after a splice.

A further object of the invention is to provide a web tension controlsystem which alleviates the dancer hunting problem.

, Yet another object of the invention is to provide a web tensioncontrol system which assures that a splice is made only when the runningweb is at a standstill.

A further object of the invention is to provide a web tension controlsystem which is relatively easy and inexpensive to make and maintain.

Still another object of the invention is to provide a web tensioncontrol system which responds quickly to an emergency situation such asa web break.

Yet another object of the invention is to provide a web tension controlsystem which enables the operator to maintain close control over theposition of the dancer in the accumulator during all phases of operationof the web supply apparatus, including emergency stops.

Other objects will in part be obvious and will in part appearhereinafter. The invention accordingly comprises'the features ofconstruction, combination of elements and arrangement of parts which areexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

We will describe the present system in conjunction with a web supplyapparatus of the type disclosed in the aforesaid patent. The apparatusincludes arbors for supporting a roll of running web and a roll of readyweb. Both rolls, or more particularly the arbors there- 'for, areequipped with brakes to -vary the speed at which the rolls turn when webis being pulled from them. The running web is fed through an accumulatorto the web-consuming machine, i.e., a printing press. In theaccumulator, the web is looped between movable dancer rolls andstationary rolls, with the amount of material in the accumulator beingdetermined by the position of the dancer.

During normal operation of the apparatus, the webconsuming machine pullsweb out of the accumulator with a force sufficient to maintain the webat a selected, substantially constant velocity, depending upon therequirements of the web-consuming machine. The position of the dancer iscontinuously measured by a pontentiometer whose resistance is employedas a basis for modulating the braking force applied to the roll ofrunning web to maintain a selected tension in the web.

The system also determines dancer velocity at each instant and thismeasurement is used to further modulate the braking force applied to thesupply roll to minimize instabilities and the tendency of the dancer tohunt about its selected zero position point.

Still further, the size of the roll of running web is measuredcontinuously. This is not done by measuring the size of the rolldirectly by a follower arm. Rather, it is done by obtaining the ratio ofthe angular velocities of a fixed guide roll ahead of the accumululatorand the running roll and employing that measurement to vary the gain ofthe system to reduce the braking force applied to the running roll asthe roll size diminishes. This gives improved braking control for webrolls of all diameters and over a full range of web speeds from threadspeed up to full speed emergency stops. This variable gain feature alsotends to maintain the dancer at its selected zero position point so thatthere is no tendency for the dancer to move down, decreasing the websupply in the accumulator as the roll size diminishes.

When the size of the running roll reaches a selected minimum size, thesystem automatically activates the splice cycle to decelerate therunning web, make the actual splice at a time when the web is stoppedand acclerate the ready web to running speed. This is accomplished witha minimum delay between these steps so that a' good splice is made in ashort time. Consequently, the system conserves a maximum amount of webstorage during the splice cycle.

The aforesaid controls over web tension and web and dancer movements areachieved substantially entirely by electronic means. Therefore, thesystem responds very quickly to changing conditions. Moreover, theelectronic components which make up the present tension control systemare more reliable and require less maintenance than the pneumatic andmechanical elements found in the prior apparatus.

BREIF DESCRIPTION OF THE DRAWINGS For a fuller understanding of thenature and objects of the invention, reference should be had to thefollowing detailed description taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a diagrammatic view of web supply apparatus incorporating thepresent invention; and

FIG. 2 is a block diagram partly in schematic form showing the tensioncontrol system in the FIG. 1 apparatus in greater detail.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to FIG. 1 of thedrawings, a roll 10 of running web is supported for rotation on asuitable shaft or arbors 12. The web W from roll 10 is conducted througha splicing station 14 and under a guide roll 16 to an accumulator showngenerally at 18. The web leaving the accumulator is conducted under aguide roll 22 and thence to the web-consuming machine, ilustratively aprinting press 24. During normal operation, a pull roll in press 24pulls web W with a force which is sufficient to give the web a fixedvelocity V into the press.

The apparatus also includes a roll 26 of ready web also rotativelysupported on a suitable shaft or arbors 28. The leading end of roll 26is set in the splicing station to await the depletion of the runningroll 10. Whereupon it is spliced to the trailing end of the running webas described in the aforesaid patent so that web proceedsuninterruptedly through the accumulator 18 into the press 24. Theactivation of the splice cycle will be described later.

A conventional tachometer 32 is geared to an arbor 12. The tachometerdevelops an output signal which is proportional to the velocity ofarbors 12 and, hence, roll 10. This signal is coupled to a controlconsole 34 and processed in the manner to be described later. A similartachometer 36 is geared to an arbor 28 to apply a signal to the console34 which is proportional to the velocity of roll 26.

A third tachometer 38 is geared to the guide roll 16 and generates anoutput signal to console 34 which is proportional to the velocity ofroll 16. Control console 34 processes the signals from tachometer 38 andfrom either tachometer 32 or tachometer 36 to develop a control signalwhich represents the instantaneous size of the roll of running web,i.e., either roll 10 or roll 26.

'The accumulator 18 comprises a set of fixed rolls 42 and a set ofdancer rolls 44 in a movable dancer 46 situated directly above rolls 42.The rolls 42 and 44 are staggered so that the web W can be looped aroundthe rolls festoon fashion so that an appreciable amount of web can bestored in the accumulator. The amount of web stored in this mannerdepends upon the distance between the dancer 46 and the fixed rolls 42.As the spacing increases, more web is stored in the accumulator and viceversa.

The dancer 46 carrying the rolls 44 is supported by suitable means suchas a cable 52 which extends up vertically and is passed around a pulley54 positioned above the fixed rolls 42. The cable extends around asecond pulley 56 and is attached to a rod 58 of a piston which includesa cylinder 62. The full stroke of the piston causes the dancer 46 tomove from its lowermost position adjacent the fixed rolls 42 to an upperposition wherein the accumulator stores a maximum amount of web W. Inpractice, differential pulleys or other means may be employed so thatthe stroke of the piston can be considerably less than the stroke ofdancer 46. A solenoid valve 63 feeds air to or bleeds air from the upperchamber within cylinder 62 (i.e., above the piston). Normally, aconstant pressure is applied to the piston which is sufficient tosupport the dancer 46 above rolls 42.

A potentiometer 66 is geared to pulley 54 so that a full stroke of thedancer 46 varies the resistance of the potentiometer over its completerange. Thus, the instantaneous position of the dancer 46 is reflected bya selected resistance value in potentiometer 46 which is applied to andprocessed by console 34 as will be described later.

During normal operation, the dancer 46 seeks a zero position Y andstores enough web in the accumulator to supply the press 24 when the webinput to the accumulator stops during the splicing cycle. At this time,press 24 pulls the web W with a force sufficient to maintain theconstant running speed V This force necessary to remove the web atconstant velocity is the sum of the inertia force caused by rolls 42 and44 and the drag force at the running roll, i.e., roll 10. Since theinertia force is substantially constant, if constant web tension is tobe maintained, then the drag force at the running roll must be varied asthe pulling force by the press varies. This is accomplished at roll by apneumatically operated disc brake 72 connected by an air line 74 toconsole 34. A similar brake 76 controls the speed of the ready web roll26, the. fluid for this brake beingapplied from the console through afluid line 78.

' Thus, during normal operation, changes in web tension are reflected bya movement of the dancer 46 up or down from its zero position Y Theinstantaneous dancer position isin turn reflected by a given resistancein the potentiometer 66. This causes the console 34 to vary the pressureapplied to the brake 72 controlling ready web from roll 26 against thetrailing edge of the running web W, the ready web having previously beenlaid into the splicing station 14 and provided with double-facedadhesive as described in the aforesaid patent. The two webs now beingspliced together, the control console 34 actuates a knife which cuts therunning web immediately behind the splice. Thereupon, the console emitsa signal to a conventional eddy current drive 82 associated with thearbors 28 supporting the roll 26 of ready web. Drive 82 accelerates theready roll for a predetermined time sufficient to bring the ready websubstantially up to the web running speed V A similar drive 84 isassociated with arbors 12 for accelerating those arbors when theyare'supporting a roll of ready web.

During the aforesaid splice cycle, the amount of web W entering theaccumulator 18 is much less than the amount of material being pulledfrom the accumulator by. press 24. Accordingly, the supply of web storedin the accumulator is reduced, causing the dancer 46 to move down towardthe fixed rolls42. Upon completion of the splicing cycle, console34controls the speediof the web entering the accumulator and the movementsof thedancer to control the rate at which the accumulator refills withWeb. In other words, if the supply of web is substantially depleted, thedancer is returned to the running web to increase or decrease the dragforce on the running web as necessary to return the dancer to its zeroposition Y I I As will be seen later also, the console processes theresistance value of potentiometer 66 to develop a signal whichrepresents the velocity of the dancer 46. This signal is also used tomodulate the drag force applied by brake 72 to obtain even closercontrol over web tension andthe movements'of dancer 46. Stillmorecontrol over web tension and dancer movements is obtained by varying thegain of the closed servoloopin the console in accordance with the sizeof roll of running web by processing the signals from tachometers 32 and38. As a result, the system minimizes the hunting movements of thedancer over the full range of web speeds. Also, just the proper amountof braking force is applied to the running web roll for the existentoperating conditions.

When the size of the running roll 10 reaches a prede termined minimumdiameter, this is detected by console 34 which thereupon initiates thesplicing cycle. The console applies a constantly increasing pressure tothe break 72 on the running roll so that the roll decelerates at apredetermined rate. By varying the gain of the system in accordance withroll size, asthe roll diminishes in size, the dancer can be made tomoveup, making more storage available at time of splice. Also, as the rolldiminishes in size, less storage is required for emergency stops.Accordingly, this system can be programmed so that just enough reservestorage is available in the accumulator to handle an emergency stopproportional to roll diameter.

As soon as the speed of the running web W reaches zero or a selectedminimum speed, as measured by the tachometer 38, console 34 emits acontrol signal to the splicing station 14 to bring the leading edge ofthe its zero position Y at a faster rate than if there is only a smallweb deficiency in the accumulator. Since a closed loop servocontrolsystem is employed, there'is much closer control over the movements ofdancer 46, particularly during the splice service cycle when theaccumulator is being refilled.

As will be described presently, the system also provides means fordetecting excessive movements of the dancer 46 which signal someemergency condition such as a web break. In response to these emergencyconditions, this'system stops the webin a controlled fashion in aminimum of time. All of these factors make the present system preferableto the prior pneumatic tension control systems exemplified in theaforesaid patent.

Referring now to FIG. 2 which shows in greater detail the components inconsole 34, the present system measures running roll size indirectly bytachometers which measure the angular velocities of the running roll andthe fixed speed guide roll 16. This can be done because the followingrelationship holds:

which filters the signal to eliminate tachometer noise and provides gainso that the output from the amplifier 92 reflects the RPM of the runningroll. A similar circuit 94 conditions the output of tachometer 38. Thesignals from circuits 92 and 94 are applied to an analog divider 96whichdivides the latter by the former to de velop an output voltagewhich reflects the instantaneous size of the running roll, e.g., roll10.

The output of the analog divider 96 is applied to an amplitudecomparator 98 which compares this voltage with the voltage from anadjustable splice radius threshold control 102. The voltage output ofcontrol 102 represents the running roll size at which it is desired tocommence the splice cycle. When the voltage applied to comparator 98 bythe divider drops to this value, indicating that the roll of running webis almost depleted, the output of comparator 98 actuates a currentdriver 104 which energizes a relay 106 to commence the deceleration ofthe running web in preparation for the splice as described above.

The output of circuit 94 indicative of the speed of the guide roll 16and, hence, the speed of the web entering the accumulator 18, is appliedto a second amplitude comparator 108 where it is compared with thevoltage from a velocity threshold control 110. When the speed of roll 16falls to zero or a selected minimum value at which a satisfactory splicecan be formed, comparator 108 develops an output which activates thedriver 11 2 controlling a relay 114. The relay, in turn, initiates theevents in the splicing operation described in the aforesaid patent.Thus, the splice is accomplished the instant that the running web stopsafter commencement of the splicing cycle. The relay 114 also engages theeddy current drive 82 which immediately accelerates the ready web 26following the splice. Thus, there is minimal delay between the varioussteps in the splicing cycle.

The output of the analog divider 96 which reflects the instantaneoussize of the roll of running web is also used to vary the gain of thecontrol system so that the braking force applied to the roll of runningweb is varied in accordance with the amount of material on the roll.More particularly, the output of the divider 96 is applied to amultiplier 122 whose other input is a voltage tension command T,developed as will be described presently by measuring the instantaneousposition of dancer 46 (FIG. 1). This is because the tension force on webW due to the application of brake 72 varies linearly with the drag forcecaused by the brake. However, the drag force does not vary linearly withthe pressure applied by the transducer 126 to the brake. Rather, thedrag force varies in accordance with the pressure divided by the radiusof the running roll 10. In the present system, a linear variationbetween the commanded tension T and resultant paper tension T isachieved by multiplying the commanded tension T, by the radius r of rollin multiplier 122. The output of multiplier 122 then controls a currentdriver 124 which drives the pressure transducer 126 operating the brake72.

When the roll on the lower set of arbors 28 is the running roll, theoutput of multiplier 122 is applied to a similar current driver 128which drives a transducer 130 associated with brake 76. Thus, thepressure applied to the brake controlling the running web roll alwaysreflects the size of the roll. For a given tension command, thispressure becomes less as the roll becomes smaller because less dragforce is necessary to maintain the same amount of tension in the web.

Still referring to FIG. 2, to develop the tension command T theresistance value of potentiometer 66 is used to measure the position ofdancer 47. More particularly, the voltage developed across thepotentiometer is applied to an amplifier 150 having a variable offsetcontrol 152 which sets the dancer zero position Y The output of theamplifier 150 is a positive or negative voltage reflecting the deviationof the dancer from its zero position Y This voltage is applied by way ofa switchable attenuator 154 to a resistor 156 which forms one leg of asumming network shown generally at 158. Attenuator 154 is switched toincrease the gain of the circuit to brake the running roll to a haltduring an emergency stop situation by a FAST STOP signal applied to itsterminal 155 as will be described later.

The voltage across the potentiometer 66 is also applied to adifferentiator 162 whose output represents the rate at whichthe dancer47 is moving at any given time. This signal is amplified by an amplifier164 and applied by way of a second switchable attenuator 166 to thesumming circuit 158 through the summing resistor 168.

The net voltage at network 158 represents the tension command T Thisvoltage is applied via a normally closed switch 172 and an amplifier 174to the multiplier 122 as noted above.

During normal operation of the apparatus, switch 172 is closed and thegain of the servoloop is such that as the dancer moves away from itszero position Y in response to a change in web tension, a tensioncommand T is issued which, when multiplied by the radis r, of therunning roll, applies just the right braking force to restore the propertension condition in the web and return the dancer to its zero position.The desired tension T can be set by way of an operator-controlledvariable resistor 176 in the summing network 158 which is connected to asuitable positive voltage source.

The inclusion of dancer velocity feedback in the servoloop whichdevelops the tension command T introduces a damperinto the system sothat proper selection of position and velocity gains in the servoloopresults in a well-behaved system. For example, in a typical apparatus, a10 pound change in web tension results in a dancer 46 displacement ofonly one inch. The preferred system is designed with unity gain so thatthere is minimal overshoot of the dancer 46 when it changes position.

When, for one reason or another, it is desired to brake the running webto a stop very quickly, a FAST STOP signal is applied to terminal 155.This changes the gain of the system so that the system responds asthough there were a rapid decrease in web tension by greatly increasingthe tension command voltage applied to multiplier 122. This, in turn,results in rapid increase in the brake pressure applied to brake 72controlling the running web. It is important to note at this point thatthe braking force applied to the running roll during an emergency stopis still modulated by the size of the running roll. Therefore, morebraking force is applied for a large roll than for a smaller roll.Consequently, a roll of any size is brought to a stop in a controlledfashion in a minimum amount of time.

When the running roll is almost depleted, a COM- MENCE SPLICE signalfrom relay 106 opens switch 172 disconnecting the summing network 158from the amplifier 174. The signal also closes a switch 184 whichapplies the output of a ramp generator 186 to the amplifier. The voltageramp from generator 186 causes the transducer 126 to apply a graduallyincreasing pressure on brake 72 controlling the running web so that theroll stops at a predetermined rate.

When the running web reaches zero speed (or a selected minimal speed),the relay 114 initiates the splicing sequence and then activates theeddy current drive associated with the ready web roll 26 whichsupplements the acceleration given the ready roll by the pulling forceof the web. The eddy current drive is turned off when the ready webreaches some selected percentage of running web speed V usually on theorder of 70-90 percent as will be described presently.

As the ready roll 26 is being accelerated, the dancer 46 continues tomove down for a time because there is still a net loss of web from theaccumulator 18. Then it moves upward as the accumulator refills. Sincethere is a danger that the dancer might bottom or move up too far, theattenuator 166 in the dancer velocity feedback branch is changed toincrease gain and thus increase velocity damping. This limits theacceleration of the dancer during its downward movement and'also as itmoves upwards during the splice service cycle. This high gain conditionis initiated at the'beginning of the roll acceleration by a signal fromrelay 114 applied to attenuator 166 by way of a HOLD circuit 191.Circuit 191 switches the attenuator 166 back to normal after 30-60seconds. By this time, the dancer is close to its zero position YAlternatively, the attenuator 166 can be turned on for a selected timeinterval after cessation of the COMMENCE SPLICE signal.

The point at which the ready web has reached the desired speed is sensedby detecting when the dancer 46 is at rest or has a certain minimumvelocity. More particularly, the output of amplifier 164 whichrepresents dancer velocity is applied to a pair of dancer velocitydetectors 192 and 194. Detector 192 generates an output signal when thedancer is moving upwards at a rate less than a predetermined magnitude,while detector 194 generates a similar output when the downward velocityof the dancer is less than a predetermined magnitude. An output fromboth detectors simultaneously thus signifies that the dancer is at restor is moving at a velocity which is within a certain acceptance bandsignifying that the ready web is at the desired percentage of runningspeed V,,.' This coincidence is detected by an AND circuit 196 whoseoutput opens a switch 198 which deenergizes a relay 202 controlling thedrive 82 associated with the ready web roll 26.

The signal from amplifier 164 representing dancer velocity is also usedto detect when an emergency condition exists such asa break in the webW. When the web breaks, there is a drastic decrease in web tension whichcauses the dancer 46 to move up rapidly away from fixed rolls 42. In thepresent system, the output of amplifier 164 is applied to an amplitudecomparator 204 which also receives an output voltage from a velocitythreshold control 206. When the voltage from circuit 164 exceeds thethreshold velocity, comparator 204 actuates a driver 208 which closes arelay 210. The closing of the relay 210 can be arranged to brake therunning roll to a stop or to control the air pressure applied tocylinder 62 biasing the dancer 46 to slow down the dancer before itreaches its upper and lower limit stops. I 8

The variable gain feature of the present system allows one to controlthe amount of reserve storage remaining in the accumulator 18 foremergency stops in accordance with roll size. In other words, the amountof necessary reserve storage becomes less as the roll diameterdecreases. Therefore, the output of the divider 96 can be applied tovary the zero position control 152 so that the zero osition Y of thedancer is lowered as the runquires a minimum amount of maintenance ascompared with prior pneumatic tension control systems. Furthermore,there is less inertia and inherent delays in the present system so thatmuch closer control can. be maintained over web and dancer movements.Furthermore, the electrical components consisting in large part ofstandard operational amplifiers and other stock components, arerelatively inexpensive to make.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

It is also to beunderstood thatv the following claims are intended tocover all of the generic and specific features of the invention hereindescribed.

We claim: v

1. Web handling apparatus comprising A. means for supporting a roll ofrunning web,

B. means for pulling web from the roll at a selected speed,

C. means for braking the roll,

D. means for sensing changes in the tension of the web as it runs causedby changes in the pulling force on the web,

E. means for controlling the braking means in accor-' dance with theoutput of the tension change sensing means so as to tend to maintainsubstantially constant web tension,

F. means responsive to the instantaneous size of the roll, and

G. means for modulating the control of the braking means so that thedrag force imparted by the brake to the web is substantially independentof roll size.

2. Web handling apparatus as defined in claim 1 wherein the sizeresponsive means comprise A. means for measuring the angular velocity ofthe roll of running web,

B. means for measuring the angular velocity of a fixed diameter rollengaged by the running web',

C. means for processing the two roll velocities to obtain a ratio whichreflects the size of the roll of running web.

3. Web handling apparatus as defined in claim 2 wherein A. the rollvelocity measuring means comprise tachometers driven by the rolls, and

B. the processing means comprise a divider which divides the output ofthe tachometer associated with the fixed diameter roll by the output ofthe tachometer associated with the roll of running web.

4. Web handling apparatus as defined in claim 1 wherein the means forsensing changes in web tension comprise I A. a deflectible member,

1. having a selected spring constant, and 2. engaged by the running webso that the web moves the member in one direction when its tensionincreases and moves the member in another direction when its tensiondecreases, and

B. means for sensing the position of the member to develop an output tocontrol the braking means.

5. Web handling apparatus as defined in claim 1 wherein A. thedeflectible member is a dancer in a web accumulator situated downstreamfrom the roll of running web, and

B. the position sensing means is a potentiometer associated with thedancer which changes its resistance value as the dancer moves inresponse to changes in web tension.

6. Web handling apparatus as defined in claim 5 and further including A.means for measuring the instantaneous velocity of the dancer,

B. means for applying the velocity measurement as a damping factor inthe brake controlling means so as to increase the braking force on theroll of running web as dancer velocity increases.

7. Web handling apparatus as defined in claim 6 and further including A.means for actuating the braking means so as to decelerate the roll ofrunning web to a selected minimum speed at a programmed rate, and

B. means for detecting when the web speed is below a predeterminedvalue.

8. Web handling apparatus as defined in claim 7 wherein the web speeddetecting means comprise A. a tachometer associated with a roll engagedby the running web, and

B. means for detecting when the output of the tachometer falls below apredetermined value.

9. Web handling apparatus as defined in claim 7 wherein the actuatingmeans comprise a ramp generator.

10. Web handling apparatus as defined in claim 6 wherein A. the dancervelocity measuring means comprise means for differentiating'a signalreflecting the potentiometer resistance value, and

B. the applying means include a summing network that sums the output ofthe differentiator with the output provided by the potentiometer.

11. Web handling apparatus as defined in claim 8 and further includingA. means for supporting a roll of ready web, and

B. means for accelerating the ready roll supporting means after the webspeed falls below said predetermined value.

12. Web handling apparatus comprising A. means for supporting a roll ofrunning web,

B. means for supporting a roll of ready web,

C. means for pulling web selectively from said roll at a selected speed,

D. means for braking the rolls,

E. a deflectible member contacting the running web and around which therunning web moves,

F. means for sensing the position of the deflectible member, saidsensing means emitting a signal when the member deviates from a selectedposition,

G. means for differentiating the signal from the position sensing means,

H. means for summing the outputs of the position sensing means and thedifferentiating means, and

l. means for controlling the braking means in accordance with the outputof the summing means so as to tend to maintain substantially constanttension in the running web.

13. Web handling apparatus as defined in claim 12 and further includingmeans for modulating the output of the summing means in accordance withthe size of the roll of running web so that the braking force applied tothe running roll varies inversely with the size of the running roll.

14. Web handling apparatus as defined in claim 13 wherein the modulatingmeans comprise A. means responsive to the diameter of the running webroll and emitting an output signal in response thereto, and

B. means for multiplying the output of the responsive means by theoutput of the summing ,means prior to the application of the latter tothe brake control means.

15. Web handling apparatus as defined in claim 14 wherein the runningweb roll diameter detecting means comprise A. means for measuring theangular velocity of the running web roll,

B. means for measuring the angular velocity of a fixed diameter roll incontact with the running web,

C. means for dividing the output of the first angular velocity measuringmeans by the output of the second angular velocity measuring means, and

D. means for multiplying the quotient of said division by the output ofthe summing means prior to application of the latter to the brakecontrol means.

16. Web handling apparatus as defined in claim 13 further including A.means for measuring the speed of the running web and delivering anoutput signal in response thereto, and

B. means responsive to the output of the modulating means forcontrolling the brake control means so as to brake the running web rollto a selected minimum speed when the running web roll diameter reaches apre-determined minimum size.

17. Web handling apparatus as defined in claim 16 comprising A. meansfor accelerating the roll of ready web after the running web rollreaches said selected minimum speed, and

B. means for disabling the accelerating means after the ready web rollreaches a pre-determined higher speed.

18. Web handling apparatus as defined in claim 17 wherein the disablingmeans include A. a first detector means responsive to the output of thedifferentiating means for emitting an output when the velocity of thedeflectible member in one direction from the selected position is lessthan a minimum value,

B. second detector means responsive to the output of the differentiatingmeans for emitting an output when the velocity of the deflectible memberin the opposite direction from the selected position is less than saidminimum value, and

C. means for disabling the accelerating means up on the simultaneousoccurrence of outputs from the two detector means.

19. Web handling apparatus as defined in claim 18 further includingmeans responsive to the output of the differentiating means for causingthe brake control means to brake the running web roll to a stop when thevelocity of the deflectable member exceeds a selected maximum value.

It is a: a:

Disclaimer 3,822,838.Richard A. Butler, Jr., Chestnut Hill and Jack TIHansen, Needham,

Mass., August R. Rump, Chicago, 111., and Rudy R. Arendt, South Wales,N.Y. WEB HANDLING APPARATUS. Patent dated July 9,

1974. Disclaimer filed May 1981, by the assgnee Butler Greenwich,

Inc.

Hereby enters this disclaimer to clailfis l to 5 of said patent.

[Oflicial Gazette August 4, 1981.]

1. Web handling apparatus comprising A. means for supporting a roll ofrunning web, B. means for pulling web from the roll at a selected speed,C. means for braking the roll, D. means for sensing changes in thetension of the web as it runs caused by changes in the pulling force onthe web, E. means for controlling the braking means in accordance withthe output of the tension change sensing means so as to tend to maintainsubstantially constant web tension, F. means responsive to theinstantaneous size of the roll, and G. means for modulating the controlof the braking means so that the drag force imparted by the brake to theweb is substantially independent of roll size.
 2. Web handling apparatusas defined in claim 1 wherein the size responsive means comprise A.means for measuring the angular velocity of the roll of running web, B.means for measuring the angular velocity of a fixed diameter rollengaged by the running web, C. means for processing the two rollvelocities to obtain a ratio which reflects the size of the roll ofrunning web.
 2. engaged by the running web so that the web moves themember in one direction when its tension increases and moves the memberin another direction when its tension decreases, and B. means forsensing the position of the member to develop an output to control thebraking means.
 3. Web handling apparatus as defined in claim 2 whereinA. the roll velocity measuring means comprise tachometers driven by therolls, and B. the processing means comprise a divider which divides theoutput of the tachometer associated with the fixed diameter roll by theoutput of the tachometer associated with the roll of running web.
 4. Webhandling apparatus as defined in claim 1 wherein the means for sensingchanges in web tension comprise A. a deflectible member,
 5. Web handlingapparatus as defined in claim 1 wherein A. the deflectible member is adancer in a web accumulator situated downstream from the roll of runningweb, and B. the position sensing means is a potentiometer associatedwith the dancer which changes its resistance value as the dancer movesin response to changes in web tension.
 6. Web handling apparatus asdefined in claim 5 and further including A. means for measuring theinstantaneous velocity of the dancer, B. means for applying the velocitymeasurement as a damping factor in the brake controlling means so as toincrease the braking force on the roll of running web as dancer velocityincreases.
 7. Web handling apparatus as defined in claim 6 and furtherincluding A. means for actuating the braking means so as to deceleratethe roll of running web to a selected minimum speed at a programmedrate, and B. means for detecting when the web speed Is below apredetermined value.
 8. Web handling apparatus as defined in claim 7wherein the web speed detecting means comprise A. a tachometerassociated with a roll engaged by the running web, and B. means fordetecting when the output of the tachometer falls below a predeterminedvalue.
 9. Web handling apparatus as defined in claim 7 wherein theactuating means comprise a ramp generator.
 10. Web handling apparatus asdefined in claim 6 wherein A. the dancer velocity measuring meanscomprise means for differentiating a signal reflecting the potentiometerresistance value, and B. the applying means include a summing networkthat sums the output of the differentiator with the output provided bythe potentiometer.
 11. Web handling apparatus as defined in claim 8 andfurther including A. means for supporting a roll of ready web, and B.means for accelerating the ready roll supporting means after the webspeed falls below said predetermined value.
 12. Web handling apparatuscomprising A. means for supporting a roll of running web, B. means forsupporting a roll of ready web, C. means for pulling web selectivelyfrom said roll at a selected speed, D. means for braking the rolls, E. adeflectible member contacting the running web and around which therunning web moves, F. means for sensing the position of the deflectiblemember, said sensing means emitting a signal when the member deviatesfrom a selected position, G. means for differentiating the signal fromthe position sensing means, H. means for summing the outputs of theposition sensing means and the differentiating means, and I. means forcontrolling the braking means in accordance with the output of thesumming means so as to tend to maintain substantially constant tensionin the running web.
 13. Web handling apparatus as defined in claim 12and further including means for modulating the output of the summingmeans in accordance with the size of the roll of running web so that thebraking force applied to the running roll varies inversely with the sizeof the running roll.
 14. Web handling apparatus as defined in claim 13wherein the modulating means comprise A. means responsive to thediameter of the running web roll and emitting an output signal inresponse thereto, and B. means for multiplying the output of theresponsive means by the output of the summing means prior to theapplication of the latter to the brake control means.
 15. Web handlingapparatus as defined in claim 14 wherein the running web roll diameterdetecting means comprise A. means for measuring the angular velocity ofthe running web roll, B. means for measuring the angular velocity of afixed diameter roll in contact with the running web, C. means fordividing the output of the first angular velocity measuring means by theoutput of the second angular velocity measuring means, and D. means formultiplying the quotient of said division by the output of the summingmeans prior to application of the latter to the brake control means. 16.Web handling apparatus as defined in claim 13 further including A. meansfor measuring the speed of the running web and delivering an outputsignal in response thereto, and B. means responsive to the output of themodulating means for controlling the brake control means so as to brakethe running web roll to a selected minimum speed when the running webroll diameter reaches a pre-determined minimum size.
 17. Web handlingapparatus as defined in claim 16 comprising A. means for acceleratingthe roll of ready web after the running web roll reaches said selectedminimum speed, and B. means for disabling the accelerating means afterthe ready web roll reaches a pre-determined higher speed.
 18. Webhandling apparatus as defined in claim 17 wherein the disabling meansinclude A. a first detector means Responsive to the output of thedifferentiating means for emitting an output when the velocity of thedeflectible member in one direction from the selected position is lessthan a minimum value, B. second detector means responsive to the outputof the differentiating means for emitting an output when the velocity ofthe deflectible member in the opposite direction from the selectedposition is less than said minimum value, and C. means for disabling theaccelerating means up on the simultaneous occurrence of outputs from thetwo detector means.
 19. Web handling apparatus as defined in claim 18further including means responsive to the output of the differentiatingmeans for causing the brake control means to brake the running web rollto a stop when the velocity of the deflectable member exceeds a selectedmaximum value.